Oxidation is the main cause of food spoilage. During storage and transportation, foods are spoiled and degraded by microorganisms. Foods also chemically react with oxygen in the air, causing them, especially oils or fats, to deteriorate. This not only reduces food nutrition, but also deteriorates flavor and color. This also produces harmful substances that endanger human health. Therefore, adding an appropriate amount of antioxidants to foods is a simple and economical method to prevent oxidative deterioration of foods.
The use of antioxidants not only prolongs the storage period and the shelf life of foods, but also brings good economic benefits to producers and distributors and gives consumers a better sense of security. At present, synthetic and semi-synthetic antioxidants have attracted more and more attentions. In addition to being used alone, the antioxidants can also be used with other food additives having other functions to form a multifunctional preparation and a dosage form, for example, packaging materials with preservatives and antioxidants.
Hydroxytyrosol (4-(2-hydroxyethyl)-1,2-benzenediol; compound of formula II) is a phenylethanoid, a type of phenolic phytochemical with antioxidant properties in vitro. In nature, hydroxytyrosol is found in olive leaf and olive oil, in the form of its elenolic acid ester oleuropein and, especially after degradation, in its plain form.

1,6-Hexamethylene diisocyanate (HDI, compound of formula III) has excellent UV absorption capacity, and it is an important raw material for synthetic polyurethane. Because HDI does not have the structural characteristics of C═C and benzene ring, the polyurethane prepared from HDI has yellowing resistance and high decorative properties, widely used in coatings, adhesives, synthetic leather and other fields.
